A COMPARISON OF THERMOREGULATORY RESPONSES IN THE JAPANESE MACAQUE (MACACA FUSCATA) AND THE CRABEATING MACAQUE (MACACA IRUS) DURING COLD EXPOSURE

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Abstract
Thermoregulatory responses in four male adult Japanese macaques and four male adult crab-eating macaques, weighing 6-12 kg and 6.2-8 kg, respectively, were compared at ambient temperatures (Ta) ranging from 5 degrees C to 25 degrees C. The average values +/- S.E. for some physiological measurements made at Ta of 25 degrees C in the Japanese macaque and the crab-eating macaque, respectively, were as follows: resting metabolic rate; 47.6 +/- 5.0 and 42.5 +/- 1.7 W/M2; tissue conductance; 11.9 +/- 0.8 and 8.9 +/- 0.8 W/M2/degrees C; respiratory evaporative heat loss; 4.1 +/- 0.3 and 3.2 +/- 0.5 W/M2; rectal temperature; 38.6 +/- 0.1 and 37.4 +/- 0.2 degrees C; mean skin temperature; 34.0 +/- 0.3 and 31.2 +/- 0.1 degrees C. When Ta was lowered stepwise from 25 degrees C to 20, 15, 10, and 5 degrees C successively, and maintained constant at each temperature level for 1 hr, metabolic heat production graudually increased in both species. Whe Ta was lowered from 10 degrees C to 5 degrees C, the crab-eating macaque did not show further increase in heat production and the result was a loss of thermal equilibrium with rectal temperature continuing to fall. On the other hand, the Japanese macaque maintained thermal balance even at Ta of 5 degrees C. Tissue conductance, which was significantly higher in the Japanese macaque than in the crab-eating macaque at Ta of 5, 15, and 25 degrees C, decreased in both species at Ta was lowered from 25 degrees C to 15 and 5 degrees C. The specific differences in thermo-regulatory responses are considered to be adaptational, relative to the natural habitat of thw two species studied.

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